GrazFeed FAQ

FAQ

1. Does GrazFeed work?

Yes, GrazFeed is the computerised and easily useable version of the recommendations in the report published as ‘Feeding Standards for Australian Livestock. Ruminants’ by the Standing Committee on Agriculture in 1990. Revisions to the Standards, which are incorporated in current versions of GrazFeed, were published by CSIRO in 2007 in ‘Nutrient Requirements of Domesticated Ruminants’. GrazFeed has been used widely by advisors and farmers since its first release in 1990.
While improvements to the functions in GrazFeed are continually made as new information becomes available, the accuracy of its estimates also depends largely on the accuracy of inputs provided by the user to describe the available pasture, supplements and livestock.

2. Where does GrazFeed work?

GrazFeed can be used wherever cattle and sheep graze pastures. GrazFeed is suitable for both temperate and tropical pastures but is not designed for rangelands where shrubs and isolated plants make up most of the vegetation. A wide range of sheep and cattle breeds can be described in terms of the animal’s type, mature live weight, age and reproductive status.

3. Can I use an old GrazFeed input file in the new version of GrazFeed?

Previous GrazFeed analyses that have been saved as *.gfi files can be opened and run in the new version of GrazFeed. To open a *.gfi file go to File/Open on the main GrazFeed toolbar.

4. How do I export a GrazFeed file?

Input files can be saved to a directory of your choice and have a filename extension *.gfi. Use your file manager software to browse to the input file of interest and copy or send the file from there.

5. Where do I get information about pasture descriptions for GrazFeed?

Pastures are described in terms of the green and dead herbage available for grazing (weight of Dry Matter per hectare), quality (Dry Matter Digestibility as a percentage) and legume content (as a percentage of Dry Matter). These values can be measured but are more commonly estimated visually. Visual estimates can be quite accurate after some training, which is available in Australia through PROGRAZE courses delivered by state Departments of Agriculture and private consultants. Users can also adjust values for the protein content, height and distribution of pasture mass into different digestibility pools. Note that the measured mass of herbage is that removed by cutting with a shearing handpiece at ground level. This cutting method leaves a residue of pasture that is accounted for in GrazFeed calculations.

6. What’s the difference between GrazFeed and GrassGro?

GrazFeed calculates the energy and protein requirements from pasture and supplement of one class of grazing ruminants for one day. GrassGro simulates pasture and animal production for a whole sheep or cattle enterprise through time (days, months or years). GrassGro enables different management options to be tested over several seasons and provides a gross margin analysis. The animal model embedded within GrassGro is the same as that used in GrazFeed. GrazFeed is a ruminant nutrition calculator, while GrassGro is a tool to analyse more complex management, production risk and land capability issues and requires training to use efficiently.

7. What kind of problems can I solve with GrazFeed?

GrazFeed can be used to help answer questions about sheep and cattle production such as “How much live weight will these animals gain or lose on this pasture?”, “Will animals reach a particular live weight target if I provide a supplement?”, “How much supplement should I feed?”, “What is the effect on weight gain if the quality of the supplement is changed?”, “What will be the growth rate of young unweaned animals if their dams graze this pasture?”, “How many animals will this paddock support in the short term?”.

8. How do I get a new version of GrazFeed?

GrazFeed is available from CSIRO. Go to this page for details.

9. How do I measure my pasture?

There are two ways of getting reasonably precise estimates of the weight of herbage (in tonnes of dry matter/ha) on a paddock: visual assessment and pasture meters.
Both of these methods need to be checked or calibrated by cutting, weighing and drying herbage from a few small areas at the same time.
Visual assessment: Visual estimation is probably the most practicable for the farmer or advisor. One or more observers walk over the paddock and, at randomly selected sites, they make a total of about 20 visual estimates of the weights (tonnes DM/ha) of green and dead material and the percentage of legume. The average of these estimates for each component is then calculated. Until an estimator becomes quite experienced with his/her particular pastures, it is necessary to calibrate these visual estimates against measured weights from cut samples.
The weight of pasture to enter into GrazFeed is that removed by cutting with a shearing handpiece at ground level. This cutting method leaves a residue of pasture that is accounted for in GrazFeed calculations.
Pasture meters: Pasture meters can be used to estimate the weight of herbage but they will not help you to estimate the different components in the pasture: green, dead and legume. These will still have to estimated visually or from a sorted sample collected over the whole paddock. There are two main types of meter: the rising (or falling) plate meter and the electronic capacitance meter. The first type estimates herbage weight through the responsiveness of a metal disk to the height and density of the herbage. The second estimates it through the electrical capacitance of the herbage. Both types of meter require calibration.

10. How do I use the results of laboratory feed analyses in GrazFeed?

In GrazFeed the metabolizable energy (ME) content of pasture is estimated from the user’s description of the digestibile dry matter content (DMD%) of green and dead herbage and legume content (%). Default values for the crude protein content of pasture can be modified by the user.
Feed analysis services may report on feed quality characteristics for forage and supplements that are not required for GrazFeed. GrazFeed uses metabolizable energy (ME) as the basis for energy requirements and, if the user considers that a sample of feed differs from the default composition, the program will predict its ME content from its digestibility and ether extract concentration. This regression equation has a very low error term, and is much better than a prediction based on neutral detergent fibre (NDF) or acid detergent fibre (ADF) content.

Default values for feed quality for a range of supplements are built into GrazFeed but can also be modified by the user. Concentrate (grain) supplements in GrazFeed are descibed in terms of their dry matter content (DM%), digestible dry matter content (DMD%), metabolizable energy concentration (ME:DM), crude protein (CP%), and rumen degradable protein content (RDP%). Additional information on acid detergent insoluble protein (ADIP, as a % of CP)and ether extract (as a % of DM) are also used to describe supplements.
Roughage feeds (hay and silage) are too variable for the default values in GrazFeed to be more than a rough guide. Laboratory analysis can be very useful here or you may need to seek advice in assessing the quality of your feed. The digestibility and protein content of roughages are likely to be somewhat lower (depending on weather conditions during conservation) than those of the herbage from which it was made. As a general guide, protein degradability is likely to be about 10 percentage units higher than the DM digestibility.
If you have had silage analysed for dry matter (DM)% and dry matter digestibility (DMD)% and these values were obtained after oven drying, then adjustments should be made (as shown in the GrazFeed Help file) to allow for the loss of volatile, but useful, nutrients that occurs during oven drying.